Embossed microporous membrane battery separator materials and methods of manufacture and use thereof

ABSTRACT

Disclosed are embossed microporous membranes, as well as articles (e.g., battery separators, materials, textiles, composites, and laminates) comprising the embossed microporous membranes. Also provided are methods of making and/or using embossed microporous membranes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application to application Ser. No.14/662,629, filed Mar. 19, 2015, which claims benefit of and priority toU.S. Provisional Application No. 61/955,285 filed Mar. 19, 2014, whichis hereby incorporated herein by reference in its entirety.

FIELD OF THE APPLICATION

In accordance with at least selected embodiments, aspects or objects,this application relates to embossed or calendered battery separators,battery separator membranes or layers, microporous membrane batteryseparators, microporous membranes, composites or laminates, methods ofmanufacture, methods of use, products or systems including suchseparators, layers, membranes, composites, or laminates, and/or thelike.

BACKGROUND

Microporous membranes are known, can be made by various processes, andthe process by which the membrane is made may have an impact upon themembrane's physical attributes. See, Kesting, R., Synthetic PolymericMembranes, A structural perspective, Second Edition, John Wiley & Sons,New York, N.Y., (1985). Three commercially viable processes for makingmicroporous membranes include: the dry-stretch process (also known asthe CELGARD process), the wet process, and the particle stretch process.

The dry-stretch process refers to a process where pore formation resultsfrom stretching a nonporous precursor film. See, Kesting, Ibid. pages290-297. The dry-stretch process differs from other methods of formingmicroporous membranes, including the wet process and particle stretchprocess. Generally, in the wet process (also referred to as the phaseinversion process, the extraction process, or the TIPS process), apolymeric raw material is mixed with a processing oil (sometimesreferred to as a plasticizer). This mixture is then extruded, and theprocessing oil is removed (these films may be stretched before or afterthe removal of the oil). See, Kesting, Ibid. pages 237-286. Generally,in the particle stretch process, a polymeric raw material is mixed withparticulate. This mixture is extruded, and pores are formed duringstretching when the interface between the polymer and the particulatefractures due to the stretching forces. See, for example, U.S. Pat. Nos.6,057,061 and 6,080,507. In addition to differences in the processesused to form these membranes, the resulting membranes formed by theseprocesses may be physically distinct.

While microporous membranes, including microporous membranes made by thedry-stretch process, have met with excellent commercial success, thereis a need to improve their physical attributes so that they may be usedin an even wider spectrum of applications. In particular, there is aneed for membranes having improved machine direction (MD) tensilestrength, increased transverse direction (TD) tensile strength,increased puncture strength, and decreased MD splitting.

SUMMARY

Provided herein are embossed microporous membranes. The embossedmembranes can exhibit improved physical attributes, such as increased MDtensile strength, increased TD tensile strength, increased puncturestrength, decreased MD splitting, or a combination thereof, as comparedto identical membranes lacking embossing. The embossed microporousmembranes can also exhibit decreased membrane thickness.

The embossed microporous membranes can comprise an embossed microporouspolymer film. The embossed microporous polymer film can be formed fromany suitable polymer or blend of polymers. For example, the embossedmicroporous polymer film can be formed from a polymer selected from thegroup consisting of polyolefins, fluorocarbons, polyamides, polyesters,polyacetals (or polyoxymethylenes), polysulfides, polyvinyl alcohols,co-polymers thereof, and combinations thereof. In some embodiments, theembossed microporous polymer film can be formed from a polyolefin thatcomprises polypropylene, polyethylene, or a combination thereof. Incertain embodiments, the polyolefin can comprise an impact copolymerpolypropylene.

In some embodiments, the embossed microporous polymer film can have athickness of from 2 microns to 20 microns (e.g., a thickness of from 3microns to 12 microns, or a thickness of from 5 microns to 10 microns).

In some embodiments, the embossed microporous polymer film can have aporosity of from 20% to 65% (e.g., a porosity of from 25% to 50%, or aporosity of from 30% to 40%). The embossed microporous polymer film canhave a JIS Gurley of 500 or less. For example, in some cases, theembossed microporous polymer film can have a JIS Gurley of from 80seconds to 500 seconds (e.g., a JIS Gurley of from 100 seconds to 450seconds, or a JIS Gurley of from 150 seconds to 400 seconds).

In some embodiments, the embossed microporous polymer film can exhibit aratio of MD tensile strength to TD tensile strength of from 0.5 to 5.0.In some embodiments, the embossed microporous polymer film can have a TDtensile strength of at least 250 kg/cm² (e.g., a TD tensile strength ofat least 300 kg/cm², such as a TD tensile strength of from 250 kg/cm² to1000 kg/cm², or a TD tensile strength of from 300 kg/cm² to 1000kg/cm²). In some embodiments, the embossed microporous polymer film canhave an MD tensile strength of at least 1000 kg/cm² (e.g., an MD tensilestrength of from 1000 kg/cm² to 2000 kg/cm²). In some embodiments, theembossed microporous polymer film can have a TD shrinkage of less than6.0% at 90° C. and less than 15.0% at 120° C. In some embodiments, theembossed microporous polymer film can have a puncture strength of from200 g to 325 g.

In some embodiments, the embossed microporous polymer film can comprisea multi-ply embossed microporous polymer film (e.g., a bi-layer polymerfilm, a tri-layer polymer film, or a polymer film comprising more thanthree layers). Optionally, in some embodiments, the embossed microporousmembrane can further comprise a nonwoven (e.g., a spunbond or meltblownnonwoven material) disposed on a side of the embossed microporouspolymer film. In these embodiments, the microporous polymer film and thenonwoven can be combined through any suitable process, such as adhesiveor thermal lamination, embossing, calendering, or combinations thereof.

The embossed microporous membranes can be prepared by embossing asuitable microporous polymer film. The microporous polymer film can bemade by a dry-stretch process and may include a plurality of poreshaving a substantially round shape. The microporous polymer film canexhibit a ratio of machine direction tensile strength to transversedirection tensile strength of from 0.5 to 5.0.

The microporous polymer film can be formed from any suitable polymer orblend of polymers. For example, the microporous polymer film can beformed from a polymer selected from the group consisting of polyolefins,fluorocarbons, polyamides, polyesters, polyacetals (orpolyoxymethylenes), polysulfides, polyvinyl alcohols, co-polymersthereof, and combinations thereof. In some embodiments, the microporouspolymer film can be formed from a polyolefin that comprisespolypropylene, polyethylene, or a combination thereof. In certainembodiments, the polyolefin can comprise an impact copolymerpolypropylene.

In some embodiments, the microporous polymer film, before embossing, canhave a thickness of at least 8 microns (e.g., a thickness of from 8microns to 80 microns). In some embodiments, the microporous polymerfilm, before embossing can have a TD tensile strength of at least 175kg/cm² (e.g., a TD tensile strength of at least 225 kg/cm²). In someembodiments, the microporous polymer film, before embossing, can have aTD shrinkage of less than 6.0% at 90° C. and less than 15.0% at 120° C.

The microporous polymer film, before embossing, can have a porosity offrom 20% to 90% (e.g., a porosity of from 20% to 80%, a porosity of from40% to 90%, or a porosity of from 65% to 90%). In some embodiments, theplurality of pores in the microporous polymer film, before embossing,can have an average pore size of from 0.03 microns to 0.50 microns andan aspect ratio of from 0.75 to 1.25. In some cases, the microporouspolymer film, before embossing, can have a mean flow pore diameter of atleast 0.04 microns (e.g., a mean flow pore diameter of at least 0.05microns). In some cases, the microporous polymer film, before embossing,can have an Aquapore size of at least 0.06 microns (e.g., at least 0.08microns). In some cases, the microporous polymer film, before embossing,can have a JIS Gurley of less than 100. In certain cases, themicroporous polymer film, before embossing, can have a JIS Gurley ofless than 60.

In some embodiments, the microporous polymer film, before embossing, cancomprise a multi-ply microporous polymer film (e.g., a bi-layer polymerfilm, a tri-layer polymer film, or a polymer film comprising more thanthree layers).

In some embodiments, embossing the microporous polymer film can compriseembossing the microporous polymer film using a patterned embossingroller. The patterned embossing roller can impart an embossing patternto the embossed microporous membrane. Accordingly, in some embodiments,the embossed microporous membranes can comprise an embossed pattern thatincludes crushed or reduced thickness regions formed by the embossingprocess. The embossed microporous membranes can comprise any suitableembossing pattern. In some examples, the embossed microporous membranecan comprise an embossing pattern selected from the group consisting ofembossed horizontal lines running parallel to the TD of the film, anembossed crosshatch-type pattern at an angle relative to the MD and TDof the film, embossed circles in a pseudorandom pattern, a pseudorandomfloral pattern, and combinations thereof. In certain embodiments, theembossing pattern can comprise embossed horizontal lines runningparallel to the TD of the film. The horizontal lines can have a linewidth of from 2 microns to 10 microns. The horizontal lines can have aspacing in the MD of from one to ten times the line width.

In some embodiments, embossing the microporous polymer film can comprisecalendering, crushing or compressing at least portions of themicroporous polymer film. Calendering the microporous polymer film cancomprise calendering the microporous polymer film using unpatterned(e.g., smooth) embossing rollers. In these embodiments, the embossedmicroporous membrane can have a substantially uniform crushed or reducedthickness.

Also provided are methods of making and/or using embossed microporousmembranes. The methods can comprise (i) extruding a polymer to form anonporous precursor; (ii) biaxially stretching the non-porous precursorto form a biaxially stretched membrane, wherein the biaxial stretchingcomprises a machine direction stretching and a transverse directionstretching, the transverse direction stretching comprising asimultaneous controlled machine direction relax; and (iii) embossing thebiaxially stretched membrane to form the embossed microporous membrane.

In some embodiments, step (iii) of embossing the biaxially stretchedmembrane can comprise reducing the thickness of the biaxially stretchedmembrane. In these cases, the thickness of the embossed microporousmembrane can be from 35% to 75% (e.g., from 35% to 55%) of the thicknessof the biaxially stretched membrane. In some embodiments, step (iii) ofembossing the biaxially stretched membrane can comprise embossing thebiaxially stretched membrane using a patterned embossing roller. Inthese embodiments, the patterned embossing roller can impart anembossing pattern to the embossed microporous membrane. In someembodiments, step (iii) of embossing the biaxially stretched membranecan comprise calendering the biaxially stretched membrane. Calenderingthe biaxially stretched membrane can comprise calendering the biaxiallystretched membrane using unpatterned (e.g., smooth) embossing rollers.In these embodiments, the embossed microporous membrane may not comprisean embossing pattern (e.g., the embossed microporous membrane can have asubstantially constant thickness (e.g., ±15%, or ±10%) across themembrane).

In some cases, the methods can further comprise annealing the nonporousprecursor between step (i) and step (ii) at a temperature of fromT_(m)−80° C. to T_(m)−10° C. (where T_(m) is the melting temperature ofthe polymer). In some embodiments, the total machine direction stretchin step (ii) can be from 50-500%, the total transverse direction stretchcan be from 100-1200%, the machine direction relax from the transversedirection stretch can be from 5-80%, or a combination thereof. In someembodiments, the methods can further comprise providing a nonwoven on aside of the biaxially stretched membrane.

Also provided are articles, including battery separators (single ormultiple ply or layer separators), materials, textiles, composites, andlaminates, comprising the embossed microporous membranes describedherein. Also provided are batteries (e.g., lithium batteries) comprisingthe battery separators described herein. The batteries can comprise ananode, a cathode, and the battery separator comprising an embossedmicroporous membrane described herein disposed between the anode and thecathode. Also provided are other products or systems such as garments,HVAC materials, fuel cell humidity control membranes, proton exchangemembranes, separation materials, filtration materials, and the like.

DESCRIPTION OF DRAWINGS

FIG. 1 is photograph illustrating example embossed microporous membranesembossed using a patterned roller.

FIGS. 2A and 2B are scanning electron microscopy (SEM) images of bothsides of a microporous membrane embossed using unpatterned embossingrollers.

FIGS. 3A and 3B are SEM images of the surface (FIG. 3A) andcross-section (FIG. 3B) of a trilayer microporous membrane prior toembossing.

FIGS. 4A and 4B are SEM images of the surface (FIG. 4A) andcross-section (FIG. 3B) of a trilayer microporous membrane embossedusing unpatterned embossing rollers.

DETAILED DESCRIPTION

Provided herein are embossed microporous membranes. The embossedmembranes can exhibit improved physical attributes, such as increased MDtensile strength, increased TD tensile strength, increased puncturestrength, decreased MD splitting, or a combination thereof, as comparedto identical membranes lacking embossing. The embossed microporousmembranes can also exhibit decreased membrane thickness.

The embossed microporous membranes can be prepared by embossing asuitable microporous polymer film. Suitable microporous polymer filmsthat can be embossed to form the embossed microporous membranesdescribed above include microporous films made by dry-stretch processes,such as those described in U.S. Pat. No. 6,602,593 as well as thosedescribed in U.S. Patent Application Publication Nos. 2007/0196638,2008/0118827, 2011/0223486, and 2014/0302374, all of which are herebyincorporated by reference.

In some cases, the microporous polymer film can be a uniaxially-orientedCelgard membrane, such as those described in U.S. Pat. No. 6,602,593. Inother cases, the microporous polymer film can be a biaxially-orientedCelgard membrane, such as those disclosed in U.S. Patent ApplicationPublication Nos. 2007/0196638 and 2011/0223486. Such biaxially-orientedmembranes might, in some instances, perform better as battery separatorsthan uniaxially-oriented Celgard membranes because biaxial orientationincreases the membranes' porosity. Moreover, biaxially-oriented Celgardmembranes made from block copolymers of polyethylene and polypropylenemay have the additional advantage of exceptionally pleasant touch orhand. However, uniaxially-oriented embossed microporous membranes canalso be used to prepare embossed microporous membranes, includingbattery separators.

In one embodiment, the microporous polymer film can include a membranemade by a dry-stretch process. The membrane can comprise a microporouspolymer film made by a dry-stretch process and including a plurality ofpores. In some instances, the pores may be characterized assubstantially round shaped. In some embodiments, the plurality of poresin the microporous polymer film or membrane can have an average poresize, as measured by SEM, of from 0.03 microns to 0.50 microns. Further,the pore shape can be characterized by an aspect ratio, the ratio of thelength to the width of the pore. In some embodiments, the aspect ratioof the pores can range from 0.75 to 1.25.

The microporous polymer film or membrane can be formed from one or morethermoplastic polymers. These polymers can be semi-crystalline. In oneembodiment, the semi-crystalline polymer can have a crystallinity in therange of 20 to 80%. Examples of suitable polymers include polyolefins,fluorocarbons, polyamides, polyesters, polyacetals (orpolyoxymethylenes), polysulfides, polyvinyl alcohols, co-polymersthereof, and combinations thereof. Polyolefins may include polyethylenes(LDPE, LLDPE, HDPE, UHMWPE), polypropylene, polybutene,polymethylpentene, co-polymers thereof, and blends thereof.Fluorocarbons may include polytetrafluoroethylene (PTFE),polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene(FEP), ethylene chlorotrifluoroethylene (ECTFE), ethylenetetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF),polyvinylfluoride (PVF), perfluoroalkoxy (PFA) resin, co-polymersthereof, and blends thereof. Polyamides may include, but are not limitedto: polyamide 6, polyamide 6/6, Nylon 10/10, polyphthalamide (PPA),co-polymers thereof, and blends thereof. Polyesters may includepolyester terephthalate (PET), polybutylene terephthalate (PBT),poly-1-4-cyclohexylenedimethylene terephthalate (PCT), polyethylenenaphthalate (PEN), and liquid crystal polymers (LCP). Polysulfidesinclude, but are not limited to, polyphenylsulfide, polyethylenesulfide, co-polymers thereof, and blends thereof. Polyvinyl alcoholsinclude, but are not limited to, ethylene-vinyl alcohol, co-polymersthereof, and blends thereof.

In certain embodiments, the thermoplastic polymer can be a polyolefin,such as a polypropylene, a polyethylene, a polybutylene, apoly(4-methyl-1-pentene), or a combination thereof. In some embodiments,the thermoplastic polymer is a polyolefin selected from the groupconsisting of polypropylene homopolymers (e.g., atactic polypropylene,isotactic polypropylene, and syndiotactic polypropylene), polypropylenecopolymers (e.g., polypropylene random copolymers), polypropylene impactcopolymers, polyethylene, polyethylene copolymers, polybutylene,poly(4-methyl-1-pentene), and mixtures thereof. Suitable polypropylenecopolymers include, but are not limited to, random copolymers made fromthe polymerization of propylene in the presence of a comonomer selectedfrom the group consisting of ethylene, but-1-ene (i.e., 1-butene), andhex-1-ene (i.e., 1-hexene). In such polypropylene random copolymers, thecomonomer can be present in any suitable amount (e.g., an amount of lessthan 10 wt. %, such as from 1 to 7 wt. %).

In certain embodiments, the polyolefin can comprise an impact copolymerpolypropylene. Suitable polypropylene impact copolymers include, but arenot limited to, those produced by the addition of a copolymer selectedfrom the group consisting of ethylene-propylene rubber (EPR),ethylenepropylene-diene monomer (EPDM), polyethylene, and plastomers toa polypropylene homopolymer or polypropylene random copolymer. In suchpolypropylene impact copolymers, the copolymer can be present in anysuitable amount, but typically is present in an amount of from 5 to 25wt. %.

In some embodiments, the thermoplastic polymer can be a polyethylene.Suitable polyethylenes include, but are not limited to, low densitypolyethylene, linear low density polyethylene, medium densitypolyethylene, high density polyethylene, and combinations thereof. Incertain embodiments, the thermoplastic polymer can be selected from thegroup consisting of medium density polyethylene, high densitypolyethylene, and mixtures thereof. In certain embodiments, thethermoplastic polymer can be a high density polyethylene.

In other select embodiments, the microporous polymer film or membranecan further include other ingredients. For example, the microporouspolymer film or membrane can further include fillers (e.g., inertparticulates used to reduce the cost of the film, but otherwise havingno significant impact on the manufacture of the membrane or its physicalproperties), anti-static agents, anti-blocking agents, anti-oxidants,lubricants (e.g., to facilitate manufacture), and the like.

In other embodiments, various materials may be added to the polymers tomodify or enhance the properties of resulting membranes. Such materialsinclude, but are not limited to: (1) polyolefins or polyolefin oligomerswith a melting temperature less than 130° C.; (2) mineral fillersincluding, but not limited to, calcium carbonate, zinc oxide,diatomaceous earth, talc, kaolin, synthetic silica, mica, clay, boronnitride, silicon dioxide, titanium dioxide, barium sulfate, aluminumhydroxide, magnesium hydroxide and the like, and blends thereof; (3)elastomers including, but not limited to, ethylene-propylene (EPR),ethylene-propylene-diene (EPDM), styrene-butadiene (SBR), styreneisoprene (SIR), ethylidene norbornene (ENB), epoxy, and polyurethane andblends thereof; (4) wetting agents including, but not limited to,ethoxylated alcohols, primary polymeric carboxylic acids, glycols (e.g.,polypropylene glycol and polyethylene glycols), functionalizedpolyolefins etc.; (5) lubricants, for example, silicone, fluoropolymers,Kemamide®, oleamide, stearamide, erucamide, calcium stearate, or othermetallic stearate; (6) flame retardants for example, brominated flameretardants, ammonium phosphate, ammonium hydroxide, alumina trihydrate,and phosphate ester; (7) cross-linking or coupling agents; (8) polymerprocessing aid; and (9) any type of nucleating agents includingbeta-nucleating agent for polypropylene.

In some embodiments, the microporous polymer film or membrane, beforeembossing, can have a thickness of at least 8 microns (e.g., a thicknessof from 8 microns to 80 microns).

In some embodiments, the microporous polymer film or membrane, beforeembossing, can have an MD tensile strength of at least 600 kg/cm² (e.g.,at least 650 kg/cm², at least 700 kg/cm², at least 750 kg/cm², at least800 kg/cm², at least 850 kg/cm², at least 900 kg/cm², at least 950kg/cm², at least 1000 kg/cm², at least 1100 kg/cm², at least 1200kg/cm², at least 1300 kg/cm², or at least 1400 kg/cm²). In someembodiments, the microporous polymer film or membrane, before embossing,can have an MD tensile strength of 1500 kg/cm² or less (e.g., 1400kg/cm² or less, 1300 kg/cm² or less, 1200 kg/cm² or less, 1100 kg/cm² orless, 1000 kg/cm² or less, 950 kg/cm² or less, 900 kg/cm² or less, 850kg/cm² or less, 800 kg/cm² or less, 750 kg/cm² or less, 700 kg/cm² orless, or 650 kg/cm² or less).

The microporous polymer film or membrane, before embossing, can have anMD tensile strength ranging from any of the minimum values describedabove to any of the maximum values described above. For example, themicroporous polymer film or membrane, before embossing, can have an MDtensile strength of from 600 kg/cm² to 1500 kg/cm².

In some embodiments, the microporous polymer film or membrane, beforeembossing, can have a TD tensile strength of at least 175 kg/cm² (e.g.,at least 200 kg/cm², at least 225 kg/cm², at least 250 kg/cm², at least275 kg/cm², at least 300 kg/cm², at least 350 kg/cm², at least 400kg/cm², at least 500 kg/cm², at least 600 kg/cm², at least 700 kg/cm²,at least 800 kg/cm², at least 900 kg/cm², or at least 1000 kg/cm²). Insome embodiments, the microporous polymer film or membrane can have a TDtensile strength of 1100 kg/cm² or less (e.g., 1000 kg/cm² or less, 900kg/cm² or less, 800 kg/cm² or less, 700 kg/cm² or less, 600 kg/cm² orless, 500 kg/cm² or less, 400 kg/cm² or less, 350 kg/cm² or less, 300kg/cm² or less, 275 kg/cm² or less, 250 kg/cm² or less, 225 kg/cm² orless, or 200 kg/cm² or less).

The microporous polymer film or membrane, before embossing, can have aTD tensile strength ranging from any of the minimum values describedabove to any of the maximum values described above. For example, themicroporous polymer film or membrane can have a TD tensile strength offrom 175 kg/cm² to 1100 kg/cm².

In some embodiments, the ratio of the MD tensile strength of themicroporous polymer film or membrane to the TD tensile strength of themicroporous polymer film or membrane can be at least 0.5 (e.g., at least1.0, at least 2.0, at least 3.0, at least 4.0, or at least 5.0). In someembodiments, the ratio of the MD tensile strength of the microporouspolymer film or membrane to the TD tensile strength of the microporouspolymer film or membrane can be 6.0 or less (e.g., 5.0 or less, 4.0 orless, 3.0 or less, 2.0 or less, or 1.0 or less.

The ratio of the MD tensile strength of the microporous polymer film ormembrane to the TD tensile strength of the microporous polymer film ormembrane can range from any of the minimum values described above to anyof the maximum values described above. For example, the ratio of the MDtensile strength of the microporous polymer film or membrane to the TDtensile strength of the microporous polymer film or membrane can be from0.5 to 6.0 (e.g., from 0.5 to 5.0, or from 0.5 to 4.0).

In certain embodiments, the microporous polymer film or membrane canhave a TD shrinkage of less than 6.0% at 90° C. and less than 15.0% at120° C.

In some embodiments, the microporous polymer film or membrane can have aporosity of at least 20% (e.g., at least 40%, at least 50%, at least65%, or at least 80%). In some embodiments, the microporous polymer filmor membrane can have a porosity of 90% or less (e.g., 80% or less, 65%or less, 50% or less, or 40% or less).

The microporous polymer film or membrane can have a porosity rangingfrom any of the minimum values described above to any of the maximumvalues described above. For example, the microporous polymer film ormembrane can have a porosity of from 20% to 90% (e.g., a porosity offrom 20% to 80%, a porosity of from 40% to 90%, or a porosity of from65% to 90%).

In some embodiments, the microporous polymer film or membrane can have amean flow pore diameter (measured with Capillary Flow analysis using theASTM F316-86 standard method) of at least 0.04 microns (e.g., a meanflow pore diameter of at least 0.05 microns).

In some embodiments, the microporous polymer film or membrane can havean Aquapore size (measured using the Aquapore available through PMI(Porous Materials Inc.)) of at least 0.06 microns (e.g., at least 0.08microns).

In some cases, the microporous polymer film or membrane can have a JISGurley of less than 100 seconds. In some cases, the microporous polymerfilm or membrane can have a JIS Gurley of less than 80 seconds. Incertain cases, the microporous polymer film or membrane can have a JISGurley of less than 60 seconds.

In some embodiments, the microporous polymer film or membrane can have ahydrohead pressure (measured using the ASTM D3393-91 standard method) ofgreater than 140 psi.

The microporous polymer film or membrane can comprise a single-plymicroporous polymer film or a multi-ply microporous polymer film (e.g.,a bilayer film, a trilayer film, or a film comprising more than threelayers). Multi-ply films can be prepared using standard laminationmethods known in the art as discussed in more detail below. Multi-plyfilms can also be prepared using co-extrusion methods known in the artand discussed in more detail below. Multi-ply films can be made of pliesof the same materials or of differing materials. In one embodiment, themicroporous polymer film or membrane can comprise apolypropylene-polyethylene-polypropylene trilayer film.

Optionally, in some embodiments, the microporous polymer film ormembrane can further comprise a nonwoven (e.g., a spunbond or meltblownnonwoven material) disposed on a side of the microporous polymer film ormembrane. The nonwoven can be, for example, a polypropylene nonwoven. Inthese embodiments, the microporous polymer film and the nonwoven can becombined through any suitable process, such as adhesive or thermallamination, embossing, calendering, or combinations thereof.

In one example embodiment, a microporous polymer film or membrane cancomprise a Celgard® microporous membrane, particularly embossed blockcopolymer Z-Series membranes.

The embossed microporous membranes can be prepared by embossing asuitable microporous polymer film or membrane using any suitableembossing method. Methods of embossing suitable microporous polymerfilms are discussed in more detail below.

In some embodiments, embossing the microporous polymer film or membranecan comprise embossing the microporous polymer film using a patternedembossing roller. The patterned embossing roller can impart an embossingpattern to the embossed microporous membrane. Accordingly, in someembodiments, the embossed microporous membranes can comprise an embossedpattern that includes crushed or reduced thickness regions formed by theembossing process. In these cases, the embossed microporous membranescan comprise any suitable embossing pattern.

The embossing pattern can be selected based on the intended applicationfor the microporous membrane. For example, the embossing pattern can beselected so as to decrease MD splitting. The embossing pattern can alsobe selected so as to blunt any propagating crack tip for a tear in themicroporous membrane. In cases where the membranes will be used asbattery separators, the embossing pattern can also be selected so as tonot adversely impact the performance of an assembled batteryincorporating the separator. For example, the embossed pattern caninclude sufficient number of regions that retain their originalthickness and porosity so as to provide a membrane with suitableproperties (e.g., porosity) for use as a battery separator.

In some cases, the embossing pattern can be selected for aestheticand/or branding reasons. For example, the embossing pattern can includea company name, logo, or brand and/or an aesthetically pleasing pattern(e.g., a floral pattern). Examples of embossing patterns are describedin, for example, U.S. Pat. No. 3,855,046 to Hansen et al.; U.S. Pat. No.4,374,888 to Bomslaeger; U.S. Pat. No. 5,635,134 to Bourne et al.; U.S.Pat. No. 5,620,779 to Levy et al.; and U.S. Pat. No. 5,714,107 to Levyet al.

In some embodiments, the embossed microporous membrane can comprise anembossing pattern selected from the group consisting of embossedhorizontal lines running parallel to the TD of the membrane, an embossedcrosshatch-type pattern at an angle relative to the MD and TD of themembrane, embossed circles in a pseudorandom pattern, a pseudorandomfloral pattern, and combinations thereof. In certain embodiments, theembossing pattern can comprise embossed horizontal lines runningparallel to the TD of the membrane. This embossing pattern may reduce MDdirection splitting and/or blunt any propagating crack tip for a tear inthe microporous membrane.

In some embodiments, the embossed horizontal lines can have a line widthof less than 100 microns (e.g., less than 90 microns, less than 80microns, less than 70 microns, less than 60 microns, less than 50microns, less than 40 microns, less than 30 microns, less than 25microns, less than 20 microns, less than 15 microns, less than 10microns, or less than 5 microns). In some embodiments, the embossedhorizontal lines can have a line width of at least 1 micron (e.g., atleast 2 microns, at least 5 microns, at least 10 microns, at least 15microns, at least 20 microns, at least 25 microns, at least 30 microns,at least 35 microns, at least 40 microns, at least 50 microns, at least60 microns, at least 70 microns, at least 80 microns, or at least 90microns).

The embossed horizontal lines can have a line width ranging from any ofthe minimum values described above to any of the maximum valuesdescribed above. For example, the embossed horizontal lines can have aline width of from 1 micron to 100 microns (e.g., from 2 microns to 100microns, from 2 microns to 25 microns, or from 2 microns to 10 microns).In some cases, the embossed horizontal lines can have a spacing in theMD (i.e., a distance between adjacent parallel horizontal lines alongthe MD of the membrane) of from one to ten times the line width.

In the case of an embossed crosshatch-type pattern at an angle relativeto the MD and TD of the film, the crosshatch-type pattern can be formedfrom linear segments having the dimensions described above. In the caseof embossed circles in a pseudorandom pattern, the circles can havediameters equal to the dimensions described above.

The embossing process can involve a partial crush of the membrane in thenon-pattern area (or vice versa). The pattern area, which may be left bythe negative pattern impression on the embossing roll, can retain itsoriginal thickness, porosity, as well as its characteristic milky whitecolor (the white color results from the scattering of light within thepores of the film). For example, and not limited thereto, the partiallycrushed areas can be crushed from their original thickness to a finalthickness that is from 75% to 35% of the original thickness (e.g., from75% to 55% of the original thickness, from 55% to 35% of the originalthickness, from 40% to 30% of the original thickness, or from 70% to 65%of the original thickness). By way of example, in one embodiment, thepartially crushed areas can be crushed an original thickness ofapproximately 19-20 microns to a final thickness of approximately 13microns. The crushed or partially crushed areas may be non-porous orpartially porous or slightly less porous than the uncrushed or notpartially crushed areas.

Examples of improvements that can accompany embossing of the microporousmembranes include, but are not limited to, the creation of a pattern inthe membrane (e.g., in the battery separator or textile) throughembossing which involves partial crushing of the membrane in the patternor non-pattern area; enhancement, through the translucency which resultsfrom partial crushing of the membrane; improved tactile feel; theincrease in the membrane's strength through partial crushing (theimprovement can be seen in both the machine direction and transversedirection tensile strength and in puncture strength); stronger edges orportions; the like; and combinations thereof.

In some embodiments, embossing the microporous polymer film can comprisecalendering, crushing or compressing the microporous polymer film usingunpatterned (e.g., smooth) embossing rollers. In these embodiments, theembossed microporous membrane can have a substantially uniform crushedor reduced thickness. In these embodiments, the microporous polymer filmor membrane can be partially crushed from its original thickness to afinal thickness that is from 75% to 35% of the original thickness (e.g.,from 75% to 55% of the original thickness, from 55% to 35% of theoriginal thickness, from 40% to 30% of the original thickness, or from70% to 65% of the original thickness).

The embossed microporous polymer film can have a thickness of at least 2microns (e.g., at least 3 microns, at least 4 microns, at least 5microns, at least 6 microns, at least 7 microns, at least 8 microns, atleast 9 microns, at least 10 microns, at least 11 microns, at least 12microns, at least 13 microns, at least 14 microns, at least 15 microns,at least 16 microns, at least 17 microns, at least 18 microns, or atleast 19 microns). The embossed microporous polymer film can have athickness of 20 microns or less (e.g., 19 microns or less, 18 microns orless, 17 microns or less, 16 microns or less, 15 microns or less, 14microns or less, 13 microns or less, 12 microns or less, 11 microns orless, 10 microns or less, 9 microns or less, 8 microns or less, 7microns or less, 6 microns or less, 5 microns or less, 4 microns orless, or 3 microns or less).

The embossed microporous polymer film can have a thickness ranging fromany of the minimum values described above to any of the maximum valuesdescribed above. For example, the embossed microporous polymer film canhave a thickness of from 2 microns to 20 microns (e.g., a thickness offrom 3 microns to 12 microns, a thickness of from 2 microns to 8microns, a thickness of from 3 microns to 8 microns, or a thickness offrom 5 microns to 10 microns).

In some embodiments, the embossed microporous polymer film can have aporosity of at least 20% (e.g., at least 25%, at least 30%, at least35%, at least 40%, at least 45%, at least 50%, at least 55%, or at least65%). In some embodiments, the embossed microporous polymer film canhave a porosity of 65% or less (e.g., 60% or less, 55% or less, 50% orless, 45% or less, 40% or less, 35% or less, 30% or less, or 25% orless).

The embossed microporous polymer film can have a porosity ranging fromany of the minimum values described above to any of the maximum valuesdescribed above. For example, the embossed microporous polymer film canhave a porosity of from 20% to 60% (e.g., a porosity of from 20% to 50%,a porosity of from 25% to 50%, a porosity of from 30% to 55%, or aporosity of from 30% to 40%).

In some embodiments, the embossed microporous polymer film can have aJIS Gurley of at least 80 seconds (e.g., at least 90 seconds, at least100 seconds, at least 125 seconds, at least 150 seconds, at least 175seconds, at least 200 seconds, at least 225 seconds, at least 250seconds, at least 275 seconds, at least 300 seconds, at least 325seconds, at least 350 seconds, at least 375 seconds, at least 400seconds, at least 425 seconds, at least 450 seconds, or at least 475seconds). In some embodiments, the embossed microporous polymer film canhave a JIS Gurley of 500 seconds or less (e.g., 475 seconds or less, 450seconds or less, 425 seconds or less, 400 seconds or less, 375 secondsor less, 350 seconds or less, 325 seconds or less, 300 seconds or less,275 seconds or less, 250 seconds or less, 225 seconds or less, 200seconds or less, 175 seconds or less, 150 seconds or less, 125 secondsor less, 100 seconds or less, or 90 seconds or less).

The embossed microporous polymer film can have a JIS Gurley ranging fromany of the minimum values described above to any of the maximum valuesdescribed above. For example, the embossed microporous polymer film canhave a JIS Gurley of from 80 seconds to 500 seconds (e.g., a JIS Gurleyof from 100 seconds to 450 seconds, or a JIS Gurley of from 150 secondsto 400 seconds).

In some embodiments, the embossed microporous polymer film can have anMD tensile strength of at least 1100 kg/cm² (e.g., at least 1100 kg/cm²,at least 1200 kg/cm², at least 1300 kg/cm², at least 1400 kg/cm², atleast 1500 kg/cm², at least 1600 kg/cm², at least 1700 kg/cm², at least1800 kg/cm², or at least 1900 kg/cm²). In some embodiments, the embossedmicroporous polymer film can have an MD tensile strength of 2000 kg/cm²or less (e.g., 1900 kg/cm² or less, 1800 kg/cm² or less, 1700 kg/cm² orless, 1600 kg/cm² or less, 1500 kg/cm² or less, 1400 kg/cm² or less,1300 kg/cm² or less, 1200 kg/cm² or less, or 1100 kg/cm² or less).

The embossed microporous polymer film can have an MD tensile strengthranging from any of the minimum values described above to any of themaximum values described above. For example, the embossed microporouspolymer film can have a MD tensile strength of from 1000 kg/cm² to 2000kg/cm².

In some embodiments, the embossed microporous polymer film can have a TDtensile strength of at least 250 kg/cm² (e.g., at least 300 kg/cm², atleast 350 kg/cm², at least 400 kg/cm², at least 450 kg/cm², at least 500kg/cm², at least 600 kg/cm², at least 700 kg/cm², at least 800 kg/cm²,or at least 900 kg/cm²). In some embodiments, the embossed microporouspolymer film can have a TD tensile strength of 1000 kg/cm² or less(e.g., 900 kg/cm² or less, 800 kg/cm² or less, 700 kg/cm² or less, 600kg/cm² or less, 500 kg/cm² or less, 450 kg/cm² or less, 400 kg/cm² orless, 350 kg/cm² or less, or 300 kg/cm² or less).

The embossed microporous polymer film can have a TD tensile strengthranging from any of the minimum values described above to any of themaximum values described above. For example, the embossed microporouspolymer film can have a TD tensile strength of from 250 kg/cm² to 1000kg/cm² (e.g., a TD tensile strength of from 250 kg/cm² to 900 kg/cm², ora TD tensile strength of from 300 kg/cm² to 1000 kg/cm²).

In some embodiments, the ratio of the MD tensile strength of theembossed microporous polymer film to the TD tensile strength of theembossed microporous polymer film can be at least 0.5 (e.g., at least1.0, at least 2.0, at least 3.0, at least 4.0, or at least 5.0). In someembodiments, the ratio of the MD tensile strength of the embossedmicroporous polymer film to the TD tensile strength of the embossedmicroporous polymer film can be 6.0 or less (e.g., 5.0 or less, 4.0 orless, 3.0 or less, 2.0 or less, or 1.0 or less.

The ratio of the MD tensile strength of the embossed microporous polymerfilm to the TD tensile strength of the embossed microporous polymer filmcan range from any of the minimum values described above to any of themaximum values described above. For example, the ratio of the MD tensilestrength of the embossed microporous polymer film to the TD tensilestrength of the embossed microporous polymer film can be from 0.5 to 6.0(e.g., from 0.5 to 5.0, or from 0.5 to 4.0).

In certain embodiments, the embossed microporous polymer film can have aTD shrinkage of less than 6.0% at 90° C. and less than 15.0% at 120° C.

In some embodiments, the embossed microporous polymer film can have apuncture strength of at least 200 g (e.g., at least 225 g, at least 250g, at least 275 g, or at least 300 g). In some embodiments, the embossedmicroporous polymer film can have a puncture strength of 325 g or less(e.g., 300 g or less, 275 g or less, 250 g or less, or 225 g or less).

The embossed microporous polymer film can have a puncture strengthranging from any of the minimum values described above to any of themaximum values described above. For example, the embossed microporouspolymer film can have a puncture strength of from 200 g to 325 g.

In some embodiments, the embossed microporous polymer film can comprisea multi-ply embossed microporous polymer film (e.g., a bi-layer polymerfilm a tri-layer polymer film, or a polymer film comprising more thanthree layers). Optionally, in some embodiments, the embossed microporousmembrane can further comprise a nonwoven (e.g., a spunbond or meltblownnonwoven material) disposed on a side of the embossed microporouspolymer film. In these embodiments, the embossed microporous polymerfilm and the nonwoven can be combined through any suitable process, suchas adhesive or thermal lamination, embossing, calendering, orcombinations thereof.

Methods

As generally discussed above, the embossed microporous membranesdescribed herein can be made by embossing microporous membranes preparedusing conventional methods. Methods can involve preparing a suitablemicroporous membrane or film, and embossing the microporous membrane orfilm to form the embossed microporous membrane.

In some cases, methods can comprise forming a microporous membrane by adry-stretch process where a nonporous precursor is extruded and then isbiaxially stretched (i.e., not only stretched in the machine direction,but also in the transverse machine direction). This process is discussedin great detail in U.S. Patent Application Publication Nos. 2007/0196638and 2011/0223486, which are incorporated herein by reference, anddiscussed further below.

In general, the process for making the microporous membrane can includethe steps of extruding a nonporous precursor, and then biaxiallystretching the nonporous precursor. Optionally, the nonporous precursormay be annealed prior to stretching. Optionally, the nonporous precursorcan be stretched in the machine direction prior to biaxial stretching.In one embodiment, the biaxial stretching includes a machine directionstretch and a transverse direction with a simultaneous controlledmachine direction relax. The machine direction stretch and thetransverse direction stretch can be simultaneous or sequential. In oneembodiment, the machine direction stretch is followed by the transversedirection stretch with the simultaneous machine direction relax. Thisprocess is discussed in greater detail below.

Extrusion can be generally conventional (conventional refers toconventional for a dry-stretch process). The extruder can have a slotdie (for flat precursor) or an annular die (for parison precursor). Inthe case of the latter, an inflated parison technique can be employed(e.g., a blow up ratio (BUR)). However, the birefringence of thenonporous precursor may not have to be as high as in the conventionaldry-stretch process. For example, in the conventional dry-stretchprocess to produce a membrane for the embossed battery separator witha >35% porosity from a polypropylene resin, the birefringence of theprecursor may be >0.0130; while with the instant process, thebirefringence of the PP precursor could be as low as 0.0100. In anotherexample, a membrane for the embossed battery separator with a >35%porosity from a polyethylene resin, the birefringence of the precursormay be >0.0280; while with the instant process, the birefringence of thePE precursor could be as low as 0.0240.

In some embodiments, the nonporous precursor can be one of a blown filmand a slot die film. The nonporous precursor can be a single layerprecursor formed by at least one of single layer extrusion andmultilayer extrusion, or a multilayer precursor formed by at least oneof co-extrusion and lamination

Annealing (optional) can be carried out, in one embodiment, attemperatures between T_(m)−80° C. and T_(m)−10° C. (where T_(m) is themelt temperature of the polymer); and in another embodiment, attemperatures between T_(m)−50° C. and T_(m)−15° C. Some materials (e.g.,those with high crystallinity after extrusion, such as polybutene) mayrequire no annealing.

Machine direction stretch can be conducted as a cold stretch or a hotstretch or both, and as a single step or multiple steps. In oneembodiment, cold stretching may be carried out at <T_(m)−50° C., and inanother embodiment, at <T_(m)−80° C. In one embodiment, hot stretchingcan be carried out at <T_(m)−10° C. In one embodiment, total machinedirection stretching may be in the range of 50-500%, and in anotherembodiment, in the range of 100-300%. During machine direction stretch,the precursor can shrink in the transverse direction (conventional).

Transverse direction stretching can include a simultaneous controlledmachine direction relax. This means that as the precursor is stretchedin the transverse direction the precursor is simultaneously allowed tocontract (i.e., relax), in a controlled manner, in the machinedirection. The transverse direction stretching can be conducted as acold step, or a hot step, or a combination of both. In one embodiment,total transverse direction stretching can be in the range of 100-1200%,and in another embodiment, in the range of 200-900%. In one embodiment,the controlled machine direction relax can range from 5-80%, and inanother embodiment, in the range of 15-65%. In one embodiment,transverse stretching can be carried out in multiple steps. Duringtransverse direction stretching, the precursor may or may not be allowedto shrink in the machine direction. In an embodiment of a multi-steptransverse direction stretching, the first transverse direction step caninclude a transverse stretch with the controlled machine relax, followedby simultaneous transverse and machine direction stretching, andfollowed by transverse direction relax and no machine direction stretchor relax.

Optionally, the precursor, after machine direction and transversedirection stretching can be subjected to a heat setting, as is wellknown.

In some embodiments, the dry-stretch process can include the steps of:machine direction stretching followed by said biaxial stretchingincluding said transverse direction stretching with simultaneouscontrolled machine direction relax, a second transverse directionstretching with simultaneous machine direction stretching, followed byoptional transverse direction relax.

In some embodiments, the biaxial stretching step of the dry-stretchprocess includes the simultaneous biaxial stretching of a plurality ofseparate, superimposed, layers or plies of nonporous precursor, whereinnone of the plies are bonded together during the stretching process.

In some embodiments, the biaxial stretching step of the dry-stretchprocess includes the simultaneous biaxial stretching of a plurality ofbonded, superimposed, layers or plies of nonporous precursor, whereinall of the plies are bonded together during the stretching process.

Once formed, the microporous membrane can be embossed. Embossed, as usedand described herein, may describe any embossing or calendering typeprocess of the material, including, but not limited to, beetled,watered, embossed, schreiner, the like, combinations thereof, etc.

Methods of embossing polymer films are known in the art. Any suitableembossing method can be used. The microporous films can be embossedusing heat and/or pressure to create compressed, translucent regions(e.g., partially crushed areas) that contrast with regions that retaintheir original thickness, porosity, and characteristic milky white color(the white color results from the scattering of light within the poresof the film).

The embossed regions can be imparted by one or more methods suitable forpermanently embossing thin films. By way of example only, the compressedregions can be formed using heat and/or pressure as well as othermethods such as ultrasonic energy and so forth. As a particular example,compression of selected regions of the microporous films can be achievedvia the use of patterned roller assemblies such as are commonly used inpoint bonding processes. Point bonding generally refers to the processof mechanically compressing one or more layers at numerous small,discrete points. Desirably the layers are embossed by thermal pointbonding which generally involves passing one or more layers to be bondedbetween heated rolls such as, for example, an engraved or patterned rolland a second roll. The engraved roll is patterned in some way so thatthe fabric is not bonded over its entire surface, and the second rollcan either be flat or patterned.

In some embodiments, embossing can comprise embossing the microporousmembrane or film using a patterned embossing roller. In theseembodiments, the patterned embossing roller can impart an embossingpattern to the embossed microporous membrane. Said another way, in theseembodiments, the embossing rollers can have engraved patterns on them,and the patterns can become stamped in to the embossed microporousmembrane, where the end result is a raised or sunken pattern, dependingon the roller (See, for example, FIG. 1).

In some embodiments, embossing the microporous membrane or film cancomprise calendering, crushing or compressing the microporous membraneor film using unpatterned (e.g., smooth) embossing rollers. In theseembodiments, the resulting embossed microporous membrane may notcomprise an embossing pattern (e.g., the embossed microporous membranecan have a substantially constant thickness (e.g., ±15%, or ±10%) acrossthe membrane).

In some embodiments, embossing the microporous membrane or film cancomprise reducing the thickness of the microporous membrane. In thesecases, the thickness of the embossed microporous membrane can be from35% to 75% (e.g., from 35% to 55%, from 75% to 55%, from 40% to 30%, orfrom 70% to 65%) of the thickness of the microporous membrane or film,before embossing.

Also provided are articles, including battery separators (e.g., lithiumbattery separators, such as secondary lithium battery separators,lithium ion battery separators, and/or lithium metal batteryseparators), materials, textiles, composites, and laminates, comprisingthe embossed microporous membranes described herein.

The articles can include one or more of the embossed membranes describedabove. In some embodiments, the articles (e.g., battery separators) canbe single-ply or multi-ply constructs comprising one or more of theembossed membranes described herein. Regarding the multi-plyembodiments, the embossed membranes can be one ply of the multi-plyconstruct, more than one ply of the multi-ply construct, or all of theplies of the multi-ply construct. If the membrane is less than all ofthe plies of the multi-ply construct, the multi-ply construct can beformed via a lamination process. If the membrane is all plies of themulti-ply construct, the multi-ply construct can be made via alamination process or an extrusion process such as a co-extrusionprocess.

In one embodiment, a microporous membrane film alone can be calenderedand/or embossed. In select embodiments, the microporous membrane filmcalendered and/or embossed alone to create the instant embossedmicroporous membrane battery separator may be a single ply film. Inother select embodiments, the microporous membrane film calenderedand/or embossed alone to create the instant embossed microporousmembrane battery separator may be a bi-layer film. In other selectembodiments, the microporous membrane film calendered and/or embossedalone to create the instant embossed microporous membrane batteryseparator may be a multi-ply film.

In another embodiment, the instant embossed microporous membrane batteryseparator may be a composite, laminate, or multi-layer separator orstructure including at least one microporous membrane or film embossedwith a nonwoven, including, but not limited to, a mesh, a spunbondnonwoven material, a meltblown nonwoven material, or some combinationthereof. The nonwoven used in the instant embossed battery separator maybe made from any desired material. In one embodiment, the nonwoven maybe a polypropylene (PP) nonwoven, including, but not limited to, a PPspunbond nonwoven and/or a PP meltblown nonwoven. The microporousmembrane or film and the nonwoven can be combined in any manner,including, but not limited to, through adhesive or thermal lamination,and/or the embossing or calendering process of the instant disclosure.In some embodiments, the embossed microporous membrane battery separatorcan further include a thin, pliable, polymeric sheet, foil, or filmhaving a plurality of pores therethrough.

The improved physical attributes of the embossed microporous membranescan result in, for example, battery separators exhibiting improvedstrength and/or resistance to splitting and waterproof/breathabletextiles exhibiting improved strength and/or resistance to splitting.

Also provided are batteries (e.g., lithium batteries) comprising thebattery separators described herein. The batteries can comprise ananode, a cathode, and the battery separator comprising an embossedmicroporous membrane described herein disposed between the anode and thecathode.

A method of using the embossed microporous membrane battery separatorsfor separating the anode and cathode of a battery is also provided.Methods can comprise positioning one or more of the embossed microporousmembrane battery separators described herein between the anode andcathode of a battery (e.g., a lithium battery).

By way of non-limiting illustration, examples of certain embodiments ofthe present disclosure are given below.

EXAMPLES

All materials were characterized using the following methods unlessotherwise stated. The thickness of membranes was measured with an Emvecomodel 210-A microgage bench micrometer according to the method describedin ASTM D374-99 (2004) entitled “Standard Test Methods for Thickness ofSolid Electrical Insulation,” which is incorporated herein by referencein its entirety. The porosity of membranes was measured according to themethod described in ASTM D2873-94 (1999) entitled “Standard Test Methodfor Interior Porosity of Poly(Vinyl Chloride) (PVC) Resins by MercuryIntrusion Porosimetry,” which is incorporated herein by reference in itsentirety. The tensile strength of membranes was measured according tothe method described in ASTM D882-12 (2012) entitled “Standard TestMethod for Tensile Properties of Thin Plastic Sheeting,” which isincorporated herein by reference in its entirety. Pore size and aspectratio measurements were obtained by the analysis of scanning electronmicroscopy (SEM) micrographs. % TD elongation at break refers to thepercentage of extension of a test sample along the TD of the test samplemeasured at the maximum tensile strength needed to break the sample. %Shrinkage was measured by incubating a sample in an oven at 90° C. for 1hour. Shrinkage was then measured in the MD and/or the TD. PunctureStrength is measured using Instron Model 4442 tensile tester accordingto the method described in ASTM D3763-14 entitled “Standard Test Methodfor High Speed Puncture Properties of Plastics Using Load andDisplacement Sensors,” which is incorporated herein by reference in itsentirety. The Gurley of the membranes was measured by two methods. Inthe first method defined as the Japanese Industrial Standard Gurley (JISGurley), Gurley is measured using the OHKEN permeability tester. JISGurley is defined as the time in seconds required for 100 cc of air topass through one square inch of film at constant pressure of 4.8 inchesof H₂O. In the second method, ASTM Gurley is measured according to themethod described in ASTM D726-94 (2003) entitled “Standard Test Methodfor Resistance of Nonporous Paper to Passage of Air,” which isincorporated herein by reference in its entirety. ASTM Gurley is definedas the time in seconds required for 10 cc of air to pass through onesquare inch of film at constant pressure of 4.8 inches of H₂O. Unlessotherwise stated, reference to the Gurley of a membrane in thisdisclosure refers to JIS Gurley.

The electrical resistance (“ER”) of the membranes was determined bysoaking a sample of the membrane having a known surface area in a 30% byweight, solution of KOH in water for 24 hours. The resulting sample wasthen disposed between working platinum electrodes (i.e., anode and acathode) immersed in an electrolyte of a 30%, by weight, solution of KOHin water and a direct current of known amperage (e.g., 40 milliamperes)was passed through the cell between the electrodes. The potential dropacross the film (E′) was measured with an electrometer. The potentialdrop across the cell without the microporous film disposed therein (E)was also determined using the same current. The electrical resistance ofthe microporous film is then determined using the equation:

ER=((E′−E)A)/I

where A is the surface area of the exposed film, I is the current acrossthe cell, ER is the electrical resistance of the membrane, and E′ and Eare as described above. Thermal shutdown was determined by measuring theER of the membrane while the temperature is linearly increased. Theshutdown temperature is defined as the temperature at which the ERincreases thousand-fold. Generally, a thousand-fold increase in ER issufficient for a battery separator membrane to stop thermal runaway in abattery. The rise in ER corresponds to a collapse in pore structure dueto melting of the membrane.

The membranes described in the following examples were produced byconventional dry-stretched techniques, except as noted.

Example 1—Preparation of Microporous Membranes

Membrane 1

Polypropylene (PP) resin was extruded using a 2.5 inch extruder. Theextruder melt temperature was 221° C. The polymer melt was fed to acircular die. The die temperature was set at 220° C. The polymer meltwas cooled by blowing air. The extruded precursor had a thickness of 27microns and a birefringence of 0.0120.

The extruded film was then annealed at 150° C. for 2 minutes. Theannealed film was then cold stretched to 20% at room temperature, andthen hot stretched to 228% and relaxed to 32% at 140° C. The machinedirection (MD) stretched film had a thickness of 16.4 microns, and aporosity of 25%. The MD stretched film was then transverse direction(TD) stretched 300% at 140° C. with an MD relax of 50%.

The resulting finished film had a thickness of 14.1 microns, and aporosity of 37%. The TD tensile strength of finished film was 550Kg/cm².

Membrane 2

Polypropylene (PP) resin was extruded using a 2.5 inch extruder. Theextruder melt temperature was 220° C. The polymer melt was fed to acircular die. The die temperature was set at 200° C. The polymer meltwas cooled by blowing air. The extruded precursor had a thickness of 9.5microns and a birefringence of 0.0160. HDPE resin was extruded using a2.5 inch extruder. The extruder melt temperature was 210° C. The polymermelt was fed to a circular die. The die temperature was set at 205° C.The polymer melt was cooled by air. The extruded precursor had athickness of 9.5 microns and a birefringence of 0.0330.

Two PP layers and one PE layers were then laminated together to form aPP/PE/PP tri-layer film. The lamination roll temperature was 150° C. Thelaminated tri-layer film was then annealed at 125° C. for 2 minutes. Theannealed film was then cold stretched to 20% at room temperature, andthen hot stretched to 160% and relaxed to 35% at 113° C. The MDstretched film had a thickness of 25.4 microns, and a porosity of 39%.The MD stretched film was then TD stretched 400% at 115° C. with an MDrelax of 30%.

The resulting finished film had a thickness of 19.4 microns and aporosity of 63%. The TD tensile strength of finished film was 350Kg/cm².

Membrane 3

PP resin and HDPE resin were extruded using a co-extrusion die to form aPP/PE/PP tri-layer film. The extruder melt temperature for PP was 243°C., and the extruder melt temperature for PE was 214° C. Polymer meltwas then fed to a co-extrusion die which is set at 198° C. The polymermelt was cooled by blowing air. The extruded film had a thickness of35.6 microns.

The extruded precursor was then annealed at 125° C. for 2 minutes. Theannealed film was then cold stretched to 45% at room temperature and hotstretched to 247% and relaxed to 42% at 113° C. The MD stretched filmhad a thickness of 21.5 microns and a porosity of 29%. The MD stretchedfilm was then TD stretched 450% at 115° C. with 50% MD relax.

The resulting finished film had a thickness of 16.3 microns and aporosity of 59%. The TD tensile strength of finished film was 570Kg/cm².

Membrane 4

PP resin and HDPE resin were co-extruded and MD stretched using themethod described in Example 3. The MD stretched film was then TDstretched 800% at 115° C. with 65% MD relax.

The resulting finished film had a thickness of 17.2 microns and aporosity of 49%. The TD tensile strength of finished film was 730Kg/cm².

Membrane 5

PP resin and PE resin were extruded using a co-extrusion die. Theextruder melt temperature for PP was 230° C., and extruder melttemperature for PE was 206° C. The polymer melt was then fed to aco-extrusion die which was set at a temperature of 210° C. The polymermelt was then cooled by blowing air. The extruded film had a thicknessof 36.0 microns.

The extruded precursor was then annealed at 105° C. for 2 minutes. Theannealed film was then cold stretched to 20%, and then hot stretched at105° C. to 155% and then relaxed to 35%. The MD stretched film was thenTD stretched 140% at 110° C. with 20% MD relax.

The resulting finished film had a thickness of 14.8 microns and aporosity of 42%. The TD tensile strength of finished film was 286Kg/cm².

Membrane 6

PP resin and PE resin were extruded using a co-extrusion die to form aPP/PE/PP tri-layer film. The extruder melt temperature for PP was 245°C., and extruder melt temperature for PE was 230° C. The polymer meltwas then fed to a co-extrusion die which was set at a temperature of225° C. The polymer melt was cooled by blowing air. The extruded filmhad a thickness of 27 microns and a birefringence of 0.0120.

The extruded precursor was then annealed at 115° C. for 2 minutes. Theannealed film was then cold stretched to 22% at room temperature and hotstretched to 254% and relaxed to 25% at 120° C. (total machine directionstretch=251%). The MD stretched film had a thickness of 15 microns and aporosity of 16%. The MD stretched film was then TD stretched 260% at130° C. with 50% MD relax, followed by a simultaneous MD and TD stretchof 50% and 216% in each direction at 130° C. Finally, the film was heldfast in the MD (100%) and allowed to relax 57.6% in the TD at atemperature of 130° C.

The resulting finished film had a thickness of 7.6 microns and aporosity of 52%. The TD tensile strength of finished film was 513Kg/cm².

Membrane 7

PP resin and PE resin were extruded using a co-extrusion die to form aPP/PE/PP tri-layer film. The extruder melt temperature for PP was 222°C., and the extruder melt temperature for PE was 225° C. The polymermelt was then fed to a co-extrusion die which was set at a temperatureof 215° C. The polymer melt was cooled by blowing air. The extruded filmhad a thickness of 40 microns and a birefringence of 0.0110.

The extruded precursor was then annealed at 105° C. for 2 minutes. Theannealed film was then cold stretched to 36% at room temperature and hotstretched to 264% and relaxed to 29% at 109° C. (total machine directionstretch=271%). The MD stretched film had a thickness of 23.8 microns anda porosity of 29.6%. The MD stretched film was then TD stretched 1034%at 110° C. with 75% MD relax.

The resulting finished film had a thickness of 16.8 microns and aporosity of 46%. The TD tensile strength of finished film was 1037Kg/cm².

Membrane 8

A PP-based impact copolymer was extruded to form a film. The extrudermelt temperature was 249° C. The polymer melt was fed to an extrusiondie set at 215° C. The polymer melt was cooled by blowing air. Theextruded film had a thickness of 34 microns and a birefringence of0.0116.

The extruded precursor was then annealed at 154° C. for 2 minutes. Theannealed film was then cold stretched to 30% at room temperature and hotstretched 190% and relaxed 61% at 140° C. (total machine directionstretch=159%). The MD stretched film had a thickness of 26 microns and aporosity of 40%. The MD stretched film was then TD stretched 260% at150° C. with 50% MD relax, followed by a simultaneous MD and TD stretchof 50% and 216%, respectively, at 150° C.

Properties of Membranes 1-8

Table 1 summarizes the physical properties of Membranes 1-8. Forpurposes of comparison, the physical properties of two commerciallyavailable dry-stretched films are also included: A) CELGARD® 2400(single ply polypropylene); and B) CELGARD® 2325 (tri-layerpolypropylene/polyethylene/polypropylene).

TABLE 1 Summary of the physical properties of Membranes 1-8. TD TensileMD Tensile MD/TD Tensile TD Thickness Strength Strength StrengthMembrane Stretching (microns) Porosity (kg/cm²) (kg/cm²) Ratio A — 25.437% 160 1700 10.6 B — 25.1 40% 146 1925 13.2 1 300% 14.1 37% 550 10131.8 2 400% 19.4 63% 350 627 1.8 3 450% 16.3 59% 570 754 1.3 4 800% 17.249% 730 646 0.9 5 140% 14.8 42% 286 1080 3.8 6 418% 7.6 52% 513 1437 2.87 1034%  16.8 46% 1037 618 0.6 8 450% 17 73% 287 558 1.9

Example 2—Microporous Membranes Embossed with a Pattern

A commercially available 19 micron thick polypropylene microporousmembrane (CG1) was embossed with a pseudorandom floral pattern using anembossing roll. The physical properties of the embossed membrane aresummarized in Table 2 below. For purposes of comparison, the physicalproperties of two samples of CG1 are also included.

TABLE 2 Summary of the physical properties of an embossed microporousmembrane. Change Change CG1 CG1 Embossed vs. vs. (sample 1) (sample 2)CG1 Sample 1 Sample 2 Thickness ≈19 19.9 13.1 −30% −34% (microns)Puncture 124 122 166 +35% +36% Strength (g) MD Tensile 560 378 846 +51%+124%  Strength (kg/cm²) TD Tensile 277 234 369 +33% +58% Strength(kg/cm²)

The embossed membrane exhibited substantially improved machine direction(MD) tensile strength, transverse direction (TD) tensile strength, andpuncture strength. In addition, embossing provided other benefits,including stronger edges and decreased MD splitting. As shown in FIG. 1,the embossing formed a visible pattern in the membrane. The white areasin the pattern are uncrushed regions of the membrane while thetranslucent (gray) areas in the pattern are partially crushed regions.The embossed membranes also exhibited a more fabric-like appearance.

Example 3—Microporous Membranes Embossed Using Unpatterned EmbossingRolls

A commercially available 15 micron thick polypropylene microporousmembrane was embossed using unpatterned embossing rolls. Various processconditions, including nip pressure, nip temperature, and embossing rolltemperature, were evaluated. All samples were embossed at a speed of 7.2feet per minute, an unwind tension of 0 psi, and a rewind tension of 5psi. The ASTM Gurley and thickness of the resulting membranes wasevaluated. The results are included in Table 3 below.

TABLE 3 ASTM Gurley and thickness of membranes following embossing usingunpatterned embossing rolls under different processing conditions.Embossing Nip Nip Roll ASTM Rough Pressure Temperature TemperatureGurley Thickness Membrane (psi) (° F.) (° F.) (sec) (microns) 9 25 70300 1.30 14 10 50 NR 300 1.31 14 11 75 NR 300 1.41 14.5 12 100 NR 3001.38 14.3 13 25 NR 320 1.40 14.5 14 50 NR 320 1.42 14 15 75 110 320 1.4914 16 100 112 320 1.54 13 17 25 116 340 1.54 13 18 50 120 340 1.73 12.519 75 127 340 3.25 10 20 100 127 340 4.60 9 21 25 131 350 12.83 7 22 50135 350 >50 — 23 75 140 350 — — 24 100 144 350 — —Based on these evaluations, membranes 19-22 were further analyzed.

The physical properties of membranes 19-22 are summarized in Table 4below. SEM images of both sides of membrane 21 are included in FIG. 2Aand FIG. 2B.

TABLE 4 Summary of the physical properties of Membranes 19-22. AverageThickness Puncture MD Tensile TD Tensile JIS Thickness Range StrengthStrength Strength Gurley Membrane (microns) (microns) (g) (kg/cm²)(kg/cm²) (sec) 19 10.79 3.1 219 613.9 954.8 49.4 20 9.973 2.8 224.31072.98 677.4 85.1 21 7.34 6.1 228.7 1708.6 664.135 215.6 22 6.11 4.9222.6 1847.9 813.3 —

A commercially available 15 micron thick trilayerpolypropylene-polyethylene-polypropylene microporous membrane (CG2) wasembossed using unpatterned embossing rolls. A total of 25 embossingconditions (EC1-EC25, Table 5 below) utilizing various nip pressures(ranging from 100 psi to 1300 psi) and nip temperatures (21° C., 54° C.,77° C., and 104° C.) were evaluated.

TABLE 5 Summary of embossing conditions (EC1-EC25). Nip Temperature NipPressure 21° C. 54° C. 77° C. 104° C. 100 EC 1 EC 9 EC 17 EC 25 200 EC 2EC 10 EC 18 — 400 EC 3 EC 11 EC 19 — 600 EC 4 EC 12 EC 20 — 800 EC 5 EC13 EC 21 — 1000 EC 6 EC 14 EC 22 — 1200 EC 7 EC 15 EC 23 — 1300 EC 8 EC16 EC 24 —Based on these evaluations, EC1, EC2. EC3, EC4, EC9, and EC10 wereselected for further analysis.

The physical properties of embossed membranes prepared using EC1, EC2.EC3, EC4, EC9, and EC10 are included in Table 6 below. The thermalshutdown behavior of membranes prepared using EC1, EC2. EC3, was EC4 wasalso evaluated. All four membranes exhibited a shutdown temperature ofbetween 125° C. and 135° C.

TABLE 6 Summary of the physical properties of membranes prepared usingEC1, EC2. EC3, EC4, EC9, and EC10. EC1 EC2 EC3 EC4 EC9 EC10 JIS Gurley(sec) 369.25 397 708.75 2191.5 730.25 1073 Thickness (microns) 11.4 12.510.4 10.4 9.3 10.2 Max Thickness (microns) 12.4 15.4 13.9 14.7 11.1 12.9Min Thickness (microns) 10.1 9.1 8.1 8.3 7.1 8.3 % MD shrinkage 8.949.48 — — — — (90° C., 1 hour) % TD shrinkage 5.08 4.99 — — — — (90° C.,1 hour) % MD shrinkage 20.95 20.2 — — — — (120° C., 1 hour) % TDshrinkage 15.48 15.12 — — — — (120° C., 1 hour) MD Tensile Strength1395.6 1136.2 — — — — (kg/cm²) TD Tensile Strength 845.93 659.28 — — — —(kg/cm²) Puncture Strength (g) 241 277

The physical properties of embossed membranes prepared using EC1 and EC4were investigated further. The results are summarized in Table 7 below.For purposes of comparison, the physical properties of CG2 are alsoincluded. SEM images of a side and cross-section of CG2 are included inFIG. 3A and FIG. 3B. SEM images of a side and cross-section of anembossed membranes prepared using EC1 are included in FIG. 4A and FIG.4B.

TABLE 7 Summary of the physical properties of membranes prepared usingEC1 and EC4. CG2 EC1 EC4 Average Thickness 27.4 11.9 9 (microns) MDTensile Strength 610 1175 1483 (kg/cm²) TD Tensile Strength 286 648 770(kg/cm²) Puncture Strength 295 294 282 (g) % TD elongation 103 88 100 atbreak

In accordance with at least selected embodiments, aspects or objects,this application or invention relates to embossed or calendered batteryseparators, battery separator membranes or layers, microporous membranebattery separators, microporous membranes, composites or laminates,methods of manufacture, methods of use, products or systems includingsuch separators, layers, membranes, composites, or laminates, and/or thelike.

The compositions and methods of the appended claims are not limited inscope by the specific compositions and methods described herein, whichare intended as illustrations of a few aspects of the claims. Anycompositions and methods that are functionally equivalent are intendedto fall within the scope of the claims. Various modifications of thecompositions and methods in addition to those shown and described hereinare intended to fall within the scope of the appended claims. Further,while only certain representative compositions and method stepsdisclosed herein are specifically described, other combinations of thecompositions and method steps also are intended to fall within the scopeof the appended claims, even if not specifically recited. Thus, acombination of steps, elements, components, or constituents may beexplicitly mentioned herein or less, however, other combinations ofsteps, elements, components, and constituents are included, even thoughnot explicitly stated.

The term “comprising” and variations thereof as used herein is usedsynonymously with the term “including” and variations thereof and areopen, non-limiting terms. Although the terms “comprising” and“including” have been used herein to describe various embodiments, theterms “consisting essentially of” and “consisting of” can be used inplace of “comprising” and “including” to provide for more specificembodiments of the invention and are also disclosed. Other than wherenoted, all numbers expressing geometries, dimensions, and so forth usedin the specification and claims are to be understood at the very least,and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, to be construed in light of thenumber of significant digits and ordinary rounding approaches.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of skill in the artto which the disclosed invention belongs. Publications cited herein andthe materials for which they are cited are specifically incorporated byreference.

1.-33. (canceled)
 34. An embossed microporous membrane prepared by aprocess comprising embossing, calendering or compressing a microporouspolymer film comprising a plurality of pores having a substantiallyround shape.
 35. The membrane of claim 34, wherein the microporouspolymer film exhibits a ratio of machine direction (MD) tensile strengthto transverse direction (TD) tensile strength of from 0.5 to 5.0. 36.The membrane of claim 34, wherein the polymer film is made by adry-stretch process.
 37. The membrane of claim 34, wherein the embossedmicroporous membrane exhibits increased MD tensile strength, increasedTD tensile strength, increased puncture strength, decreased MDsplitting, or a combination thereof as compared to the microporouspolymer film.
 38. The membrane of claim 34, wherein the embossedmicroporous membrane comprises an embossing pattern selected from thegroup consisting of embossed horizontal lines running parallel to the TDof the membrane, an embossed crosshatch-type pattern at an anglerelative to the MD and TD of the membrane, embossed circles in apseudorandom pattern, a pseudorandom object pattern, a logo pattern, andcombinations thereof.
 39. The membrane of claim 38, wherein theembossing pattern comprises embossed horizontal lines running parallelto the TD of the membrane; wherein the horizontal lines have a linewidth of from 2 microns to 10 microns; and wherein the horizontal lineshave a spacing in the MD of from one to ten times the line width. 40.The membrane of claim 34, wherein the microporous polymer film is formedfrom a polymer selected from polyolefins, fluorocarbons, polyamides,polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyvinylalcohols, co-polymers of the foregoing, or combinations of theforegoing.
 41. The membrane of claim 40, wherein the microporous polymerfilm is formed from a polyolefin, and wherein the polyolefin comprisespolypropylene, polyethylene, or a combination thereof.
 42. The membraneof claim 41, wherein the polyolefin comprises impact copolymerpolypropylene.
 43. The membrane of claim 34, wherein the plurality ofpores have an average pore size of from 0.03 microns to 0.50 microns andan aspect ratio of from 0.75 to 1.25; and wherein the microporouspolymer film has a porosity of from 20% to 80% and a TD tensile strengthof at least 175 kg/cm2.
 44. The membrane of claim 34, wherein themicroporous polymer film has at least one of a porosity of from 40% to90%, a JIS Gurley of less than 100 seconds, a mean flow pore diameter ofat least 0.04 microns, and an Aquapore size of at least 0.06 microns, aporosity of from 65% to 90%, a JIS Gurley of less than 60 seconds, amean flow pore diameter of at least 0.05 microns, and an Aquapore sizeof at least 0.08 microns, a thickness of at least 8 microns and a TDtensile strength of at least 225 kg/cm2, a thickness of from 8 micronsto 80 microns, and a TD shrinkage of less than 6.0% at 90° C. and lessthan 15.0% at 120° C.
 45. The membrane of claim 34, wherein themicroporous polymer film comprises a multi-ply microporous polymer film.46. The membrane of claim 34, further comprising a nonwoven disposed onat least one side of the embossed microporous membrane.
 47. An embossedmicroporous membrane comprising an embossed microporous polymer film,wherein the embossed microporous membrane comprises embossed horizontallines running parallel to the TD of the film; wherein the horizontallines have a line width of from 2 microns to 10 microns; and wherein thehorizontal lines have a spacing in the MD of from one to ten times theline width.
 48. An embossed microporous membrane comprising an embossedmicroporous polymer film, wherein the embossed microporous polymer filmhas a thickness of from 2 microns to 20 microns, a porosity of from 20%to 65%, and a JIS Gurley of 500 or less.
 49. The membrane of claim 48,wherein the embossed microporous film has a ratio of MD tensile strengthto TD tensile strength of from 0.5 to 5.0.
 50. The membrane of claim 48,wherein the embossed microporous polymer film is formed frompolyolefins, fluorocarbons, polyamides, polyesters, polyacetals (orpolyoxymethylenes), polysulfides, polyvinyl alcohols, co-polymers of theforegoing, or combinations of the foregoing.
 51. The membrane of claim48, wherein the embossed microporous polymer film has at least one of athickness of from 3 microns to 12 microns, a porosity of from 25% to50%, a JIS Gurley of from 80 seconds to 500 seconds, a TD shrinkage ofless than 6.0% at 90° C. and less than 15.0% at 120° C., a puncturestrength of from 200 g to 325 g, a TD tensile strength of at least 250kg/cm2, and an MD tensile strength of from 1000 kg/cm2 to 2000 kg/cm2.52. The membrane of claim 48, wherein the embossed microporous polymerfilm comprises a multi-ply embossed microporous polymer film.
 53. Themembrane of claim 48, further comprising a nonwoven disposed on a sideof the embossed microporous polymer film.
 54. A battery separator,material, textile, composite, or laminate comprising the membrane ofclaim
 34. 55. A battery separator, material, textile, composite, orlaminate comprising the membrane of claim
 48. 56. An embossedmicroporous membrane comprising an embossed microporous polymer film,wherein the embossed microporous polymer is a dry process film.
 57. Themembrane of claim 56, wherein the embossed microporous polymer film isformed from at least one of a polyolefin, and wherein the polyolefincomprises polypropylene, polyethylene, combinations thereof, orcopolymers thereof.
 58. The membrane of claim 56, wherein the embossedmicroporous polymer film has at least one of a thickness of from 3microns to 12 microns, a porosity of from 25% to 50%, a JIS Gurley offrom 80 seconds to 500 seconds, a TD shrinkage of less than 6.0% at 90°C. and less than 15.0% at 120° C., a puncture strength of from 200 g to325 g, a ratio of MD tensile strength to TD tensile strength of from 0.5to 5.0, a TD tensile strength of at least 250 kg/cm2, and an MD tensilestrength of from 1000 kg/cm2 to 2000 kg/cm2.
 59. The membrane of claim56, wherein the embossed microporous polymer film comprises a multi-plyembossed microporous polymer film.
 60. The membrane of claim 56, furthercomprising a nonwoven disposed on a side of the embossed microporouspolymer film.
 61. A battery separator, material, textile, composite, orlaminate comprising the membrane of claim 56.